Friday, October 27, 2006

Showers, cold. Despite a breeze with a south of east component, heavy clouds and light showers are keeping temperatures from reaching 50° in most of the Washington metro area this afternoon. Precipitation amounts through 5pm have been only 0.1" at National and 0.05" (all of which fell in the last hour) at Dulles.

Rainfall should be heavier overnight, however, as a developing low pressure area in the mid Mississippi and lower Ohio valleys gets cranked up on its way to the eastern Great Lakes by tomorrow. Following the passage of this very deep low, strong winds should bring another shot of cold air in for the rest of the weekend. The National Weather Service has issued a High Wind Watch for Saturday evening through Sunday morning for the potential of sustained winds at least 40 mph or gusts at least 58 mph throughout the local blogging area.

Pictured: One model's prediction of a very strong (980 mb) low centered over southern Canada Saturday evening. The closely-spaced isobars indicate strong winds over the Mid Atlantic area; from NCEP/NWS

Tonight and Tomorrow

Rain, then windy and colder. Rain will become heavier tonight, with temperatures steady in the upper 40s to near 50°. The rain will end as showers by mid day tomorrow. Southerly winds ahead of a strong cold front could push temperatures into the low 60s around the middle of the day, but strong northwesterly winds following the frontal passage will bring falling temperatures through the rest of the afternoon and into tomorrow night.

The RealClimate blog today revisits the issue of global cooling claims made in the 70s. Newsweek has just done a re-evaluation of their 1975 article titled, "A cooling world." They conclude in the cold light of today that huge improvements in data collection and modeling technology have made "any forecasts from 1975 as inoperative as the predictions being made around the same time about the inevitable triumph of communism." The real lesson here is: Don't get your science from the SCMSM (so-called mainstream media).

Thursday, October 26, 2006

A strong ridge of high pressure extending from northern Hudson Bay across eastern North America to Cuba continued pumping cold air into the Mid Atlantic region on Wednesday. A northwesterly breeze again gusting over 30 mph at times kept temperatures well below seasonal averages in the Washington metro area. High temperatures were 55° at National and Dulles, 54° at BWI.

Despite diminishing winds, temperatures will remain well below average today as a low pressure area becoming organized in the central Rockies and incorporating leftover moisture from what was eastern Pacific Huricane Paul brings the threat of rain late Friday into part of the weekend.

Surface weather map at 11pm last night from HPC/NCEP/NWS

Today and Tonight

Continued cold, less windy. Under mostly sunny skies, today's highs will be in the mid 50s. Overnight, clouds will increase toward morning with lows near 40° in the city, low to mid 30s in the cooler 'burbs.

Larson's Long-Range is off today, but we can take the opportunity to look at the connection, if any, between fall and winter temperatures. With both September and October running cooler than average, the question arises whether or not this indicates anything about the upcoming winter. As Matt has already noted, the relationship is quite complex.

The chart shows the September and October (SO) average temperature on the x-axis, and the following December, January, and February (DJF) average on the y-axis. The data points include the 135 years of Washington observations through last year. The solid regression line represents the best fit to the data, with the equation of the line shown in the upper left. The upward slope of the line shows that there is a positive relationship, but the correlation is very weak. The value 0.09 for R2 means that only 9% of the variability in winter average temperatures is explained by the September-October average. Note that out of the 5 coolest SO averages, there was one year with the coolest DJF average, but there was also one with the second warmest DJF. (For more on regression analysis, see the discussion of the December-January relationship posted last year.)

Tuesday, October 24, 2006

Correction: The reference to the daily high below (which did hold at 51°) should have said that it was within one degree of the record low maximum for the date. The fact checkers at PM Update have been suitably admonished to stay off the fried Coke.

Now

Cold, windy. It's "a winter's day in a deep and dark . . ." October? Returning from a weekend visit to the pig races and fried everything (including Coke) at the N.C. State Fair, PM Update finds that someone left the freezer door open.

Assisted by a northwesterly wind gusting over 30 mph, temperatures in the Nation's Capital region are struggling to reach the low 50s this afternoon, and the wind makes it feel much colder. The high hourly reading at National of 51° at 2pm, if it holds for the day (It's been back to 50° through 5pm), would be the average high for Dec. 2-4, and it misses the record low minimum for the date in 77 years of records by only 1°. The last time the daily high was below 55° was March 26.

Continued cold, breezy. Winds should die down somewhat tonight, but not enough to push lows below the mid to upper 30s in most places. Tomorrow will be partly cloudy and breezy, but not as windy as today, with highs around 54°.

Climate Corner: "Would You Like Information with Your Data and Fries?"

If you've ever done any searching in an unfamiliar subject area in the virtual haystack known as the web, you know it's often very hard to separate the golden from the garbage. RealClimate.org, the climate site run by climate scientists, announced today that they are participating in a new service by Google Co-op which allows searches to be performed using only sites which have been selected to meet some level of quality. So, if you'd rather get your climate change information from scientists instead of paid political propagandists, fiction writers, the oil industry, or Homer Simpson, try out their new search facility.